Okay, so i started a new singleplayer game on hard. i had Single player commands mod installed. i turned damage off to mess around with that mod. then when it turned nighttime i saw a spider. i went to it and it didnt attack me! it was still nighttime in the game. then i saw a few zombies and a creeper i went to the creeper it didnt explode. then i hit it and it exploded. i was on survival